With the rapid depletion of available public IPv4 addresses there has been renewed interest in 3rd Generation Partnership Project (3GPP) and the operator community for techniques to reduce the impact due to lack of public IPv4 addresses. These techniques include IPv6 deployment as well as the use of private IPv4 addresses and Network Address Translation (NAT) or Network Address and Port Translation (NAPT).
In recent discussions in 3GPP on IPv6 migration, the IPv4 depletion problem has received big interest and several operators and vendors have brought up discussions regarding NAT44 usage. Deployment scenario and problem descriptions when using NAT and Policy and Charging Control (PCC) have been documented in TR 23.975. So far it has however not been decided whether or not 3GPP should do any normative work on providing new solutions to the problems identified.
When using PCC the presence of NAT/NAPT in the network causes certain problems. One of these problems is that session binding between Rx sessions and Gx sessions in the Policy and Charging Control Function (PCRF) does not work as expected when there is NAT/NAPT between the User Equipment (UE) and the Application Function (AF).
There is thus a need for a method that addresses the problems with session binding between Rx and Gx sessions when there is NAT/NAPT between the UE and the AF.